21570457 has 4 divisors (see below), whose sum is σ = 21761460. Its totient is φ = 21379456.

The previous prime is 21570443. The next prime is 21570463. The reversal of 21570457 is 75407512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 309136 + 21261321 = 556^2 + 4611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21570457 - 2¹¹ = 21568409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21570427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 95332 + ... + 95557.

It is an arithmetic number, because the mean of its divisors is an integer number (5440365).

Almost surely, 2^21570457 is an apocalyptic number.

It is an amenable number.

21570457 is a deficient number, since it is larger than the sum of its proper divisors (191003).

21570457 is a wasteful number, since it uses less digits than its factorization.

21570457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191002.

The product of its (nonzero) digits is 9800, while the sum is 31.

The square root of 21570457 is about 4644.4006071828. The cubic root of 21570457 is about 278.3683031428.

Adding to 21570457 its reverse (75407512), we get a palindrome (96977969).

The spelling of 21570457 in words is "twenty-one million, five hundred seventy thousand, four hundred fifty-seven".